FIG. 1 graphically illustrates a wireless communication system comprising a mobile station 10, a base station 20, a reverse link 30 which represents the electromagnetic wave communication link transmitted from mobile station 10 to base station 20 and a forward link 40 which represents the electromagnetic wave communication link transmitted from base station 20 to mobile station 10.
In such a wireless communication system based on the cellular principle a service area 49 is divided geographically, as shown in FIG. 2, into a number of small areas 50, 52, 54, 56 called "cells," hence the name "cellular." In each cell there is a cell site 58, 60, 62, 64, respectively, where radio equipment known as the Base Station Transceiver Subsystem (BTS) is installed. Multiple cell layouts, such as macro cells, micro cells, and pico cells can be provided within a particular geographical area to effect a hierarchical coverage area wherein macro cells provide the largest coverage and pico cells the smallest. Pico cells may be used for inside public and business buildings; special area coverage, e.g., campus, stadium, airport and shopping mall; supplementing macro or mini cells with hole-filling and capacity enhancement of hot spots; temporary coverage for special events or areas hit by natural disasters; or outlying remote locations.
As shown in FIG. 3, a BTS 66' provides a link to mobile subscribers or a mobile station 10. BTSs 66 and 66' are coupled to a Base Station Controller (BSC) 70 and may include one or more antennas 67 and 67'. Multiple BTSs 66 may be coupled to a single BSC 70. Each BSC 70 is coupled to a Mobile Switching Center (MSC) 72 and the MSC 72 is in turn coupled to a Public Switched Telephone Network(PSTN) 68.
As shown in FIG. 4, a conventional BTS 66 comprises five major functional blocks: an RF Front-End 74, a plurality of Transceivers 76, a plurality of MODEM Processors 78, a Controller 80, and a Battery Backup Unit 82 comprising a multiplicity of batteries. Controller 80 interfaces with BSC 70 over a T1 or E1 line 81, and RF Front-End 74 is connected to the antennas 67 which are typically mounted at the top of a tower or pole.
In a typical system, the five major functional blocks shown in FIG. 4 are contained in one or more physical housings. The housings are typically hermetically sealed enclosures used to package and protect the internal electronic equipment from adverse environmental effects and unauthorized access. While the electronics may be located in a main chamber, the batteries of battery backup unit 82 are typically enclosed in a battery chamber separated and sealed from the main chamber to meet industrial standards.
Since BTS units 66 are installed outdoors as well as indoors, where ambient temperatures can range from -40.degree. C. to +50.degree. C., a heating/cooling temperature management system is required to regulate the internal enclosure temperature between +5.degree. C. to +65.degree. C. during BTS operation. Conventional base station heating/cooling temperature management systems have utilized a single step cooling/heating process with a compressor-driven cooling system or a conventional flat-plate heat exchanger. Such systems have encountered high failure rates and high maintenance costs. Also, these systems are unnecessarily large and heavy, making transportation, installation and removal extremely difficult, and, especially with compressor-driven cooling systems, unnecessary amounts of power are consumed. Additionally, since the batteries of the battery backup unit 82 are enclosed in a separate chamber from the main chamber 110, the batteries receive no special heating and cooling (due to isolation from the main chamber 110).
Thus, what is needed is a heating/cooling system for a base station which eliminates the need for a compressor-driven cooling system and which concurrently provides heating and cooling temperature management of the battery chamber as well as the main chamber.